Figure 5. Normalized change between future and historic simulations (\(100\times\frac{\text{future}-\text{historic}}{\text{historic}}\)) for the 41 HPEs analyzed. Events are sorted by the change in rainfall accumulation (blue bars). Dashed lines represent average inter-event values (written also inside the legend). The non-normalized changes are shown in Fig. S4. Correlations between the change in rainfall accumulation and the three other parameters are in Fig. S5.
3.3.1 Spatial Concentration of Future Rainstorms
To better understand the changes in the rain area, we examine its changes using a range of rain rate thresholds. Divergent changes in the extent of areas exceeding various rain rates are essential in understanding possible hydrological responses to climate change (Bacchi & Ranzi, 1996; Fowler, Lenderink, et al., 2021; Peleg et al., 2018). Fig. 6a displays the event-average areal rainfall coverage for each HPE with different rain rate thresholds, normalized by the largest coverage for each intensity for both historic and future simulations. The fraction of events with larger areal coverage for each rain rate threshold in historic events, i.e., the relative number of points below the 1:1 line, is displayed in Fig. 6b. The areal coverage of rainfall with relatively low rain rates (0.1-5 mm h-1) is reduced significantly for future compared to historic simulations. The opposite case is true for high rain rates (20-100 mm h-1). This change occurs at rain rates of ~10 mm h-1, where no significant change is documented between rain area above this threshold in historic and in future simulations.
These different trends imply that when compared with historic rainstorms, the total “wet” area in future events is lower, and the storms are more concentrated around the higher rain rates. This conclusion is further strengthened by the change in the autocorrelation pattern of convective rainfall, which demonstrate a much sharper decrease with distance in future compared with historic simulations and, accordingly, the median of the autocorrelation distance decreases from 8 km to 5 km (Fig. S6).